Passphrase Generator

How passphrase strength works

Strength is measured in bits of entropy: the base-2 logarithm of how many equally likely phrases could have been generated. Each random word drawn from a list of N words adds log2(N) bits, and you multiply that by the number of words for the total. Bigger word list, more words, more entropy.

This generator’s word list

This tool draws from a compact built-in list of common English words (roughly 90 of them), so each word adds about 6.5 bits. A 5-word phrase is therefore around 33 bits, and the optional two-digit number adds about 6 more. That is fine for low-stakes, memorable logins, but it is well below what you want for a master password. For high-value secrets, use more words, pair the phrase with a password manager, and prefer a full Diceware list.

Reference word lists and their entropy

Using a full 7,776-word Diceware list (12.9 bits per word):

• 4 words ≈ 51.6 bits (modest)
• 6 words ≈ 77.4 bits (strong)
• 8 words ≈ 103.2 bits (master-password grade)

How entropy compares to cracking effort

• 50 bits, resists most online attacks; crackable offline by a motivated adversary in months.
• 70 bits, resists offline cracking with current hardware for years.
• 90 bits, beyond current bulk-cracking capabilities for the foreseeable future.
• 120 bits, exceeds the security of AES-128 keys, which are generated from 128 bits of randomness.

Why random words beat a “complicated” short password

A 10-character mixed password like Xp!9k@Lm3* has about 66 bits of entropy if truly random. A 6-word passphrase like correct-horse-battery-staple-pine-kelp from a full Diceware list has 77 bits. The passphrase is stronger, easier to type, and easier to remember. The famous xkcd comic explains the intuition: humans are terrible at generating entropy manually, so we produce predictable “complicated” passwords that crackers have seen millions of times.

Tips

• Memorise the first two or three words by imagery. Build a weird mental picture connecting the words. The rest follows.
• Don’t reuse across accounts. A passphrase is only as safe as the weakest site that stores it. Use a manager and unique phrases per login.
• The appended number helps only a little. Adding two digits raises entropy by about 6 bits; it is no substitute for adding more words.
• Treat master passphrases differently. For password-manager masters and disk encryption, use 7 or more words from a full Diceware list, not the compact built-in one.

What doesn’t help

• Capitalising random letters. Adds negligible entropy, hurts memorability.
• Adding a single symbol. Adds a few bits only if its position is also random. Barely worth it.
• Substituting letters for numbers (“p@ssw0rd”). Cracking tools have handled these substitutions since the 2000s. No real improvement.